JPH0830146B2 - Conductive silicone composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a silicone composition having conductivity,
More specifically, the present invention relates to a silicone composition excellent in processability that does not lose plasticity even when carbon black is highly filled for the purpose of obtaining high conductivity.

(Prior Art) Silicone compositions that harden into silicone rubber have been well known in the past, and by utilizing their excellent properties such as weather resistance, heat resistance, cold resistance, and electrical insulation, electrical and electronic parts can be utilized. It is widely used as potting material, coating material, molding material for molding, etc. In addition, a silicone composition, which is originally an insulating material, is given conductivity and used.

As described above, as a method of imparting conductivity to a silicone composition, a method of blending conductive carbon black is generally known. For example, JP-A-54-139659
The publication describes a conductive organopolysiloxane elastomer in which a furnace black and an acetylene black having a specific surface area of 40 to 100 m ² / g are used in combination, and the publication 55-120656 discloses a surface area of 900 m ² / g. A liquid organopolysiloxane composition containing carbon black in which hollow shell-shaped particles are present in an amount of g or more is
JP-A No. 6-120761 discloses an extrusion-molding type liquid organopolysiloxane composition in which carbon black and conductive fibers are used in combination, and JP-A No. 56-120761 discloses a silicone rubber composition using a carbon black having a specific surface area of 80 m ² / g or more. Is listed.

Carbon black used for the purpose of imparting conductivity as described above, thermal black by the manufacturing method,
It is classified into types such as furnace black and acetylene black. Among these, acetylene black has a high purity and is therefore widely used as a filler for imparting conductivity to general rubber, including dry batteries.

(Problems to be Solved by the Invention) However, in the silicone rubber composition as described above, when it is desired to obtain high conductivity, it becomes difficult to mix it with the base polymer due to an increase in the amount of carbon, and for example, a mirable In type silicone rubber,
The plasticity of the unvulcanized compound increases, the flowability of the compound during molding decreases, the flow into the mold, extrudability,
There is a problem that the roll workability is significantly deteriorated.

The present invention has been made to address such a problem, and in a silicone rubber composition provided with conductivity by blending acetylene black, it has an appropriate degree of plasticity or viscosity, and has an operation during molding. The purpose of the present invention is to provide a conductive silicone composition having excellent properties.

[Structure of the Invention] (Means and Actions for Solving the Problems) As a result of repeated studies to achieve the above-mentioned object, the present inventor has used acetylene as a raw material as carbon black,
Produced by the exothermic decomposition method, hydrochloric acid absorption amount of 12ml / 5g or less, and by using iodine adsorption amount of 50mg / g or less, it was found that the above-mentioned object is achieved, the present invention It came to be done.

That is, the present invention is a conductive silicone composition containing carbon black, wherein the carbon black has a hydrochloric acid absorption amount of 12 ml / 5 g or less, and an iodine adsorption amount of 5
It is characterized by being acetylene black of 0 mg / g or less.

The conductive silicone composition of the present invention is basically a polyorganosiloxane composition which becomes a rubber elastic body when cured at room temperature or by heating, etc., to a carbon black satisfying the above conditions and, if necessary, various additives. Etc. are mixed and uniformly dispersed.

The acetylene black used in the present invention imparts excellent conductivity and appropriately suppresses the plasticity or viscosity of the compound composition. It is a characteristic component in the present invention, and has a hydrochloric acid absorption amount of 12 ml / 5 g or less and an iodine adsorption amount of 50 mg / g or less. The meanings of these quality characteristics are as follows.

In other words, the hydrochloric acid absorption amount specified in JIS K 1469 (acetylene black) is an index showing the degree of development of the structure "chain structure of carbon primary particles", and
It is known that the iodine adsorption amount specified in JIS K 1474 "Powdered activated carbon test method" is an index showing the strength of the structure. Here, when imparting conductivity to the rubber composition, that the structure is developed, that is, the amount of hydrochloric acid absorbed is large, and that structure is strong,
That is, the larger the amount of iodine adsorbed, the higher the secondary contact probability of carbon, and the structure is less likely to be broken by the stress caused by mixing or kneading. However, according to the present invention, it has been clarified that a silicone-based polymer, which is much softer than other organic polymers, does not have the same general idea and requires an appropriate structure to enable uniform dispersion. It is.

That is, in order to impart good workability to the compound or composition, and to give good conductivity, the hydrochloric acid absorption amount of acetylene black is 12 mg / g or less, and the iodine adsorption amount is 50 mg / g. It is necessary to provide good workability and good conductivity even when any of the values exceeds the above values.

On the other hand, the polyorganosiloxane composition, which is the main component of the silicone rubber composition of the present invention, contains (a) a polyorganosiloxane base polymer, (b) a curing agent, and various additives as necessary, It is evenly dispersed.

Among various components used in such a polyorganosiloxane composition, the (a) silicone base polymer and (b) curing agent are appropriately selected according to the reaction mechanism for obtaining the rubber-like elastic body. is there. As the reaction mechanism, a crosslinking method using an organic peroxide vulcanizing agent, a condensation reaction method, an addition reaction method, etc. are known. Depending on the reaction mechanism, the components (a) and (b), that is, for curing It is well known that the preferred combination with catalyst or crosslinker will be determined.

That is, when the above crosslinking method is applied, the base polymer of the component (a) is usually a polydiorganosiloxane in which at least two of the organic groups bonded to silicon atoms in one molecule are vinyl groups. Is used. Further, the curing agent of the component (b) includes benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxy. Various organic peroxide vulcanizing agents such as hexane and di-t-butyl peroxide are used, and since they give particularly low compression set, dicumyl peroxide and cumyl-t-
Butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane and di-t-butyl peroxide are preferred. In addition, these organic peroxide vulcanizing agents are 1
It is used as a kind or a mixture of two or more kinds.

The blending amount of the organic peroxide which is the curing agent of the component (b) is
The amount is preferably in the range of 0.05 to 15 parts by weight based on 100 parts by weight of the silicone base polymer as the component (a). If the content of the organic peroxide is less than 0.05 parts by weight, the vulcanization will not be sufficiently carried out, and if it is blended in excess of 15 parts by weight, there will be no further significant effect and the physical properties of the obtained silicone rubber This is because it may have an adverse effect.

Further, in the case of applying the above condensation reaction,
As the base polymer of the component (a), polyorganosiloxane having hydroxyl groups at both ends is used. As the curing agent of the component (b), first, as a cross-linking agent, ethyl silicate, propyl silicate, methyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, methyltris (methoxyethoxy) silane, vinyltris ( Alkoxy type such as (methoxyethoxy) silane and methyltripropenoxysilane; acetoxy type such as methyltriacetoxysilane and vinyltriacetoxysilane; methyltri (acetoneoxime) silane, vinyltri (acetoneoxime) silane, methyltri (methylethylketoshikim) silane ,
Examples thereof include vinyltri (methylethylketoxime) silane and the like, and partial hydrolysates thereof. Also, hexamethyl-bis (diethylaminoxy) cyclotetrasiloxane, tetramethyldibutyl-bis (diethylaminoxy) cyclotetrasiloxane, heptamethyl (diethylaminoxy) cyclotetrasiloxane, pentamethyl-
Cyclic siloxanes such as tris (diethylaminoxy) cyclotetrasiloxane, hexamethyl-bis (methylethylaminoxy) cyclotetrasiloxane, and tetramethyl-bis (diethylaminoxy) -mono (methylethylaminoxy) cyclotetrasiloxane are also exemplified. It As described above, the cross-linking agent may have any of a silane and siloxane structure, and the siloxane structure may be any of linear, branched and cyclic structures. Furthermore, when using these, it is not necessary to be limited to one type, and two or more types can be used in combination.

Among the curing agents (b), curing catalysts include iron octoate, cobalt octoate, manganese octoate, tin naphthenate, tin caprylate,
Carboxylic acid metal salts such as tin oleate; dimethyltin dioleate, dimethyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin dioleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis (tributylbis (tributyltin diacetate. Organotin compounds such as ethoxysiloxy) tin, dioctyltin dilaurate are used.

Of the curing agent (b), the amount of the crosslinking agent is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the base polymer (a). If the amount of the cross-linking agent used is less than 0.1 parts by weight, the cured rubber will not have sufficient strength, and if it exceeds 20 parts by weight, the obtained rubber will be brittle, and any of them will be difficult to put into practical use. Further, the compounding amount of the curing catalyst is preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the base polymer as the component (a). If the amount is less than this, it is insufficient as a curing catalyst, and it takes a long time to cure, and the curing in the interior far from the contact surface with air becomes poor. On the other hand, if the amount is larger than this, the storage stability will decrease. A more preferable range of the compounding amount is 0.1 to 3 parts by weight.

As the base polymer of the component (a) when the above-mentioned addition reaction is applied, the same base polymer as that described above is used. As the curing agent of the component (b), a platinum catalyst such as chloroplatinic acid, a platinum olefin complex, a platinum vinyl siloxane complex, platinum black, or a platinum triphenylphosphine complex is used as a curing catalyst. A polydiorganosiloxane having an average of at least two hydrogen atoms bonded to silicon atoms per molecule is used.

In the curing agent of the component (b), the compounding amount of the curing catalyst is
(A) 1 to 10 elemental platinum elements based on the base polymer of component
Amounts in the range of 00 ppm are preferred. If the compounding amount of the curing catalyst is less than 1 ppm as the amount of platinum element, the curing does not proceed sufficiently, and if it exceeds 1000 ppm, no particular improvement in the curing rate can be expected. The amount of the crosslinking agent is preferably such that the number of hydrogen atoms bonded to silicon atoms in the crosslinking agent is 0.5 to 4.0 per alkenyl group in the component (a),
More preferably, the amount is 1.0 to 3.0. When the amount of hydrogen atoms is less than 0.5, the curing of the composition does not proceed sufficiently, and the hardness of the composition after curing becomes low,
On the other hand, if the number of hydrogen atoms exceeds 4.0, the physical properties and heat resistance of the composition after curing will deteriorate.

The organic group in the polyorganosiloxane as the base polymer of the component (a) used in the various reaction mechanisms as described above is a monovalent substituted or unsubstituted hydrocarbon group, such as a methyl group, an ethyl group, or a propyl group. , Butyl group, hexyl group, alkyl groups such as dodecyl group,
Unsubstituted hydrocarbon groups such as aralkyl groups such as aryl groups such as phenyl groups, β-phenylethyl groups and β-phenylpropyl groups, and chloromethyl groups and 3,3,3-trifluoropropyl groups A substituted hydrocarbon group is exemplified.
In addition, a methyl group is generally used because of its ease of synthesis.

In the conductive silicone composition of the present invention, the above-mentioned curing mechanism and polysiloxane base polymer are not particularly limited, but from the viewpoint of conductive properties, addition reaction or organic peroxide vulcanization thereof is preferable. The degree of polymerization of the siloxane-based polymer is 1000 or more,
The so-called millable type is preferable. this is,
Since the shear stress at the time of mixing is moderate, it is presumed that the above-mentioned effects can be more exerted by mixing.

The compounding amount of acetylene black is arbitrarily selected depending on the degree of polymerization of the polysiloxane base polymer and the characteristics of the resulting silicone rubber composition, and is not particularly limited, but generally the polysiloxane base polymer is used.
It is used in the range of 1 to 500 parts by weight, preferably 5 to 200 parts by weight, based on 100 parts by weight.

The conductive silicone composition of the present invention may be optionally added with a filler, a pigment, a heat resistance improver, a flame retardant, etc., within the range of not impairing the effects of the present invention. Siloxane may be used together. Examples of such substances are usually fumed silica, precipitated silica, reinforcing charging agents such as diatomaceous earth, titanium oxide, aluminum oxide, zinc oxide, iron oxide, cerium oxide, mica, clay, graphite, zinc carbonate. , Manganese carbonate, cerium hydroxide, glass beads, polydimethylsiloxane, alkenyl group-containing polysiloxane, and the like.

(Example) Hereinafter, an example of the present invention will be described. In the following text, all “parts” indicate “parts by weight”.

Example 1 100 parts of polydimethylsiloxane (polymerization degree of about 6000) whose ends were blocked with trimethylsilyl groups and contained 0.15 mol% of methylvinylsiloxane units had a hydrochloric acid absorption capacity of 10 ml / 5 g as carbon black and an iodine adsorption capacity. 48 mg / g of acetylene black A was charged into a kneader at a ratio of 60 parts as shown in Table 1, kneaded and taken out after the compound was collected.

Then, as a crosslinking agent, 2,5-dimethyl-2,5-
A silicone rubber composition was prepared by uniformly mixing 2 parts of di-t-butylperoxyhexane.

Also, as a comparison with the present invention, the hydrochloric acid absorption amount is 16 ml / 5 g
Then, using carbon black having an iodine adsorption amount of 58 mg / g (acetylene black B) and carbon black having an iodine adsorption amount of 254 mg / g (furnace black C), as shown in Table 1, Comparative sample compositions (Comparative Example 1 and Comparative Example 2) were prepared in the same manner as the silicone rubber composition of Example 1.

Using each of the silicone rubber compositions thus obtained, the plasticity and the conductive properties of the obtained rubber were evaluated by the methods described below.

For composition plasticity, Williams Plasticity JI
It was measured and evaluated according to SK 6300 (unvulcanized rubber physical test method).

In addition, these compounds are made into 2mm thick sheet, and 1
After press vulcanization at 70 ° C for 10 minutes, vulcanization was performed as secondary vulcanization at 200 ° C for 4 hours, and after returning to room temperature to obtain silicone rubber sheets, a multimeter ( The volume resistivity was measured using Advantest Corporation.

 The results are shown in Table 1.

[Effects of the Invention] As described above, according to the present invention, a silicone composition containing acetylene black can satisfy both conditions of high conductivity and good workability.

Claims (1)

[Claims] 1. A conductive silicone composition containing carbon black, wherein the carbon black is acetylene black having a hydrochloric acid absorption amount of 12 ml / 5 g or less and an iodine adsorption amount of 50 mg / g or less. And a conductive silicone composition.